This castle was constructed in 1524 (Ōkubo 4) as an outpost for the rulership of Yakushima by Lord Tanegashima. Spanning the fifty years between its construction and its abandonment in 1575 (Tenshō 3), this castle saw a handful of battles as well as a brief change of hands with Lord Nejime of the Ōsumi Peninsula. Since there was no local ruler on Yakushima, these battles are thought to have been over the control of lumber and fishing on the island.
This fortress stood at an elevation of 48 meters above sea level. It was protected by earthen walls, stone walls, and a dry moat. Directly in line of sight from Tanegashima, it thus occupied a role in tying the two islands together. While the construction and operation was dictated by vassals of Lord Tanegashima, many of Kusugawa’s village people were involved in its lifetime.
Incidentally, the nearby Kusugawa Kumano shrine finds its counterpart in the Tanegashima Kumano shrine across the strait. Both are dedicated to safe birth and child-rearing.